According to JP-A-2006-144588, a fuel injection valve includes a valve element for opening and closing a fuel injection port, a backpressure control valve for controlling backpressure of the valve element, and piezo elements for actuating the backpressure control valve. When the piezo elements are charged so as to expand, the piezo elements actuate the backpressure control valve to reduce backpressure of the valve element, and thereby the valve element performs an opening operation, and fuel is injected from the injection port.
In JP-A-2006-144588, after charge of the piezo elements is started, the backpressure control valve starts operation at the time point when a voltage value of charged power exceeds a threshold value Vth (refer to FIG. 5B). Conventionally, a charge control unit for controlling electric charge of the piezo elements is typically designed such that while a drive current to be supplied to the piezo elements is repeatedly increased and decreased for several times (refer to FIG. 5A), a voltage value is increased (refer to FIG. 5B) so that the piezo elements are charged.
Here, for example, even when the amount of electric charge of the piezo elements is fixed, the piezo elements may differently expand depending on temperature in each charge operation. Moreover, because of aged deterioration such as ablation of a valve seat for the valve element or the backpressure control valve, even when the amount of electric charge of the piezo elements is fixed, the piezo elements may differently expand depending on ablation in each charge operation. That is, variation may occur in timing, at which the backpressure control valve starts operation, due to the aged deterioration or a temperature characteristic of each piezo element. Thus, variation may occur in valve opening operation timing (injection start timing) of the valve element.